FBI Releases New Images, Info From Navy Yard ShootingThe FBI offered new details Wednesday about the Sept. 16 shooting at the Navy Yard in Washington, D.C. The shooter, Aaron Alexis, was apparently delusional, believing for the three months prior to the incident that he was being controlled by extremely low-frequency electromagnetic waves. A video released of the incident shows Alexis driving into the building and then walking in stairways and halls armed with a shotgun. The FBI says was not targeting anyone in particular.

The FBI offered up more evidence today about the Washington Navy Yard shooting last week in which 12 people were killed, along with the shooter. They released surveillance videotape of the gunman, Aaron Alexis, inside the building. They also confirmed that Alexis acted alone, and that he was delusional. NPR's Tom Bowman has more.

TOM BOWMAN, BYLINE: Aaron Alexis was a government contractor with a secret security clearance, who used his pass to enter the Navy Yard on the morning of Sept. 16th. Video surveillance camera footage released by the FBI shows Alexis calmly moving down a stairwell and long hallways with a sawed-off shotgun.

VALERIE PARLAVE: Etched into the barrel of the shotgun were the words, quote, "End To The Torment," closed quote. Etched into the right side of the shotgun receiver were the words, quote, "Not What Ya'll Say."

BOWMAN: That's FBI Assistant Director Valerie Parlave. She told a news conference that there were multiple indicators that Alexis was delusional. Shortly before the massacre, Alexis wrote this electronic message.

PARLAVE: "Ultra-low frequency attack is what I've been subject to for the last three months. And to be perfectly honest, that is what has driven me to this," closed quote.

BOWMAN: Meanwhile, Deputy Defense Secretary Ashton Carter says the Pentagon will review how Alexis' behavior and brushes with the law were missed, allowing him to receive and retain a secret clearance. Security investigators missed the fact that he shot out someone's tires with a handgun in 2004.

ASHTON CARTER: Well, that jumped out at me - evidence that there was behavior well before the Washington Navy Yard incident.

BOWMAN: Carter said the Pentagon will also review whether the military should handle security clearances in-house, and not rely on private contractors to do the background checks.

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